To choose the correctly sized Rocna or Vulcan anchor for your boat, follow the chart and instructions below the chart.
1 t (metric tonne) = 1,000 kg
For multihulls: use the chart as instructed, then select the model one size larger.
1 short ton = 2,000 lb
To choose the correctly sized Rocna or Vulcan anchor, find your vessel’s length from the column on the left, then track across that row until you find the first column with a displacement (in tonnes) the same or larger than the displacement of your vessel. The top of the column with the selected displacement indicates the recommended Rocna or Vulcan anchor.
Our anchor sizing is conservative
Unlike other manufacturers, our anchor sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. For more on our philosophy and rationale, please consult our Knowledge Base article on our sizing recommendations.
This chart is a guideline only, so if you’d like further information please enquire with us for further advice.
The Rocna 150 (331 lb) and larger
We do not provide standard recommendations for boats larger than those for which the Rocna 110 (243 lb) would be the recommended size. This is because of increasing complexities of the factors involved. Furthermore, classification society rules and/or legal requirements are likely to dictate the anchor sizes mandated for these vessels.
(*) Classification Rules sizing
Rocna anchors from size 110 kg (243 lb) and above may be sized based on classification society Rules for Ships for SHHP anchors. Modern rules permit a mass 33% lighter than HHP types, or 50% lighter than “standard stockless” types. Anchor sizing is based on a vessel’s separately calculated Equipment Number (EN). For more information, please consult the Rocna Knowledge Base articles on our sizing recommendations and Classification and Certification.